This invention relates to food products, and especially to food products obtainable from oilseeds, as for example, soy beans and peanuts.
Malnutrition due to protein deficiency is a serious problem in many parts of the world. Normally humans indirectly obtain protein from vegetable material by consuming animals which consume the vegetable material. It would be more efficient if it were possible for humans to directly consume more protein in vegetable material without having to rely on animal intermediaries.
To this end, much attention has been directed to soy beans and peanuts as potential protein sources. Ordinarily soy proteins are extracted from fat-free flakes. These fat-free flakes are prepared from whole soy beans by dehulling, rolling and hydrocarbon solvent extracting the soy beans. The extracted flakes are then steamed and heated to remove traces of solvent. The flakes are usually stored until needed for extracting the protein.
Although this hydrocarbon solvent extraction method has achieved commercial success, it is not without disadvantages.
First, since the solvent extracted flakes have a large surface area and usually are stored under uncontrolled temperature and humidity conditions, the flakes may undergo many chemical changes, enzymatic and otherwise, which could lead to undesirable flavors in the flakes themselves and in products made from these flakes. Furthermore, there may be a residual off-flavor due to the hydrocarbon solvent. In addition, the use of hydrocarbon solvents leads to processing difficulties due to the flammable and explosive nature of the solvents and air pollution problems associated with hydrocarbons.
To overcome the disadvantages of hydrocarbon solvent extraction methods researchers have developed water extraction techniques. Chayen, in U.S. Pat. No. 2,928,821 describes a method of producing a protein-lipid complex from vegetable material. This process includes the steps of introducing the vegetable material into a hammermill in the presence of an aqueous liquid carrier, alkylyzing the liquid, and then acidulating the liquid to precipitate the protein-lipid complex. Chayen states that the preferred temperature of the liquid fed into the hammermill is about 45.degree.-55.degree. F.
The Chayen process does overcome some of the disadvantages of the hydrocarbon extraction process. Any residual taste from the hydrocarbons is eliminated.
However, Chayen's process has disadvantages. Only proteins and lipids, but not carbohydrates are recovered from the feed vegetable material. Also, Chayen reports a yield of less than 50% of his protein-fat complex on test with peanuts. Such low yields are of limited commercial value. Furthermore, because of the low temperatures of the Chayen process it is doubtful that lipoxidase and anti-nutritional factors such as anti-trypsin which are in soy beans would be destroyed during the process. In the literature it is stated that the undesirable flavor and odor of soy bean base beverages are probably caused by the enzyme system lipoxidase which catalyzes the oxidation of polyunsaturated oils and fats in the soy beans. The oxidation reaction takes place quickly whenever the bean cell structure is damaged as when the bean cotyledons are bruised, cracked or ground, so that the enzymes and oils are permitted to contact each other.
A high temperature, slightly acidic, aqueous solution extraction process for preparing soy milk from dehulled or presoaked beans is described by Wilkens and Hackler in "Cereal Chemistry," July 1969, Volume 46, No. 4, P. 391.
Because the Wilkens and Hackler process requires that the soy bean feed be either presoaked or dehulled, a facility using this process would have extra operating and capital costs.
The current state of the art is summarized by Smith and Circle in Soybeans: Chemistry and Technology, Vol. 1, P. 150, 1972. They state: "the bitter principle, beany taste, and color undoubtedly are the principle obstacles to the use of the soybean as a human food in the United States. Apparently these three problems are still prevalent today since Eley (1968) reports these same problems as the factors limiting the unrestricted use of soybean products in foods. During this 25 year period, many patents granted and papers published pertain to improving the flavor and color of the isolated protein. Seemingly, none of these procedures or processes have completely solved the problem."
Therefore there is a need for an economical process for producing a high protein food product derived from vegetable material which recovers substantially all of the nutritional parts of the vegetable material, and does not use hydrocarbon solvents. The resultant product should be of good initial flavor and be stable with minimal rancidity and minimal flavor development in storage. The product should be essentially free of fiber, and in the case of soy beans, as the source vegetable material, the resultant product should not have a beany flavor. The product also should be water dispersible and compatible with other food materials such as whey, so that it can be combined with these food materials to yield nutritious and palatable food stuffs.